1. Field of the Invention
This invention relates to a method and apparatus for harvesting aquaculture. More specifically, the present invention relates to the use of nets and hydraulic machinery to harvest aquaculture from a relatively confined body of water such as a pond.
2. Description of the Prior Art
While serving as a source of food, the rivers, lakes and seas have present the problem of catching fish and other life in the underwater environment for which mankind is not particularly well adapted. Tools were developed very early to assist in retrieving food from the waters. As the centuries have passed, the tools have grown both in complexity and effectiveness. Some of the more recently developed tools are illustrated in the following United States Patents:
U.S. Pat. No. 734,571--Knapp PA1 U.S. Pat. No. 1,304,302--Gage, Sr. PA1 U.S. Pat. No. 3,113,389--Vuskovich PA1 U.S. Pat. No. 3,458,947--Ross PA1 U.S. Pat. No. 3,608,217--Voisin, Sr. PA1 U.S. Pat. No. 3,777,388--Newman et al PA1 U.S. Pat. No. 1,252,500--Schnoor PA1 U.S. Pat. No. 3,473,509--Miyamura PA1 U.S. Pat. No. 3,553,879--Ellis PA1 U.S. Pat. No. 3,715,831--Mason PA1 U.S. Pat. No. 4,276,710--Yunker et al PA1 U.S. Pat. No. 3,491,474--Metalf, Jr. PA1 U.S. Pat. No. 3,415,001--Ott et al PA1 U.S. Pat. No. 3,651,595--Newman PA1 U.S. Pat. No. 3,775,891--Holt
The patents listed above all relate to devices for catching fish or the like in bodies of water too large to harvest completely. However, it has been realized that certain species of aquaculture can be raised in relatively small, confined bodies of water. Raising aquaculture in either natural or manmade confined bodies of water greatly simplifies and makes more efficient the task of harvesting the aquaculture. Just as mankind progressed from hunting to farming to help create a steady supply of food on land, aquaculture is now being raised to increase and improve the supply of seafood.
To harvest a relatively small pond, a manual technique has been commonly employed in which three or four men move a net called a wing down the length of a pond. This operation alone takes 30 to 45 minutes with a 100.times.500 foot pond. When the wing is about 100 feet from the end of the pond, the harvesting crew attaches a second net called a bag to the end of the wing. The bag is a net sewn into the shape of a topless shoebox with one end open. The crew then continues to move the end of the wing opposite the bag around the end of the pond and back towards the bag. Thus, the area in which the aquaculture are surrounded becomes smaller. As harvesting proceeds, the crew must work more and more slowly to avoid allowing the aquaculture which become increasingly dense to escape from under the wing. Eventually, the aquaculture are concentrated in the bag.
The total operation for harvesting a 100.times.500 foot pond takes three to four men 1.5 to 2 hours. Even at this slow speed, only 40 to 70 percent of the aquaculture within the pond are captured.
To improve on this manual technique, several mechanical devices have been developed to harvest aquaculture from a confined body of water. The following United States patents all teach devices to improve the harvesting of aquaculture from confined bodies of water:
Ellis, supra, discloses a seine tow bar used for drawing a net behind a pair of tractors for harvesting fish in a farm fishpond. Each tow bar has a tractor mounting hitch and a pivot arm to which a seine is attached. Attached to the opposite end of the pivot arm is a skid which rides along the bottom of the pond. As the seine is drawn through the pond, the arm pivots to follow the contour of the pond bottom so that the seine is maintained close to the bottom and the escape of fish past the seine is supposedly prevented. After the tractors proceed down the pond, the tractors then approach each other and the net is drawn in to concentrate the fish in a small area.
Yunker et al, supra, teaches drawing a single net across a rectangular pond. The net is carried by a device having a truss which is maintained above the pond by a carriage on each side. This patent teaches the use of an inclined ramp at the end of the pond to facilitate removal of the aquaculture from the pond.
These patents teach systems which are suspect with respect to efficiency due to both the possibility of aquaculture escape around the edge of the net, and also the difficulty of removing aquaculture from the pond. In Ellis, the patent drawing shows a gap between the bottom of the pond and the boom to which the net is attached. Furthermore, in Ellis, no easy method is taught for actually removing the aquaculture from the pond. The device in Yunker et al is fairly rigid. If the contours of the pond change as is typically caused by erosion or the like, gaps are created between the net and the pond. Furthermore, the ramp provided at the end of the pond requires careful construction to prevent unevenness which would cause gaps to form under the net through which aquaculture can escape.
The loss of harvesting efficiency caused by aquaculture escaping under nets has been recognized as a problem to at least a certain extent. Thus, the following United States patents all teach the use of electrodes to prevent aquaculture from escaping beneath trawling nets:
However, none of these patents teach an electrification system suitable for use in conjunction with a net for sweeping the entire volume of a relatively small pond.